diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8550e4076..8b8cde3fa 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -37,6 +37,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - use correct split of data with the `--eval val` or `--eval test` cli arguments [\#139](https://github.com/mllam/neural-lam/pull/139) @SimonKamuk
 
+- Fix step length calculation when dt >= 24h [\#141](https://github.com/mllam/neural-lam/pull/141) @deinal
+
 ### Maintenance
 - update ci/cd testing to use cuda 12.8 [\#140](https://github.com/mllam/neural-lam/pull/140) @SimonKamuk
 
diff --git a/neural_lam/datastore/mdp.py b/neural_lam/datastore/mdp.py
index f3a81b725..879f8575f 100644
--- a/neural_lam/datastore/mdp.py
+++ b/neural_lam/datastore/mdp.py
@@ -143,7 +143,8 @@ def step_length(self) -> int:
 
         """
         da_dt = self._ds["time"].diff("time")
-        return (da_dt.dt.seconds[0] // 3600).item()
+        total_sec = da_dt.dt.total_seconds().isel(time=0).astype(int)
+        return (total_sec // 3600).item()
 
     def get_vars_units(self, category: str) -> List[str]:
         """Return the units of the variables in the given category.